1. Field of the Invention
The present invention relates to a communication apparatus which operates according to an intermittent pattern of a call signal from a switching network.
1. Related Background Art
In the case of sharing one communication line between speech communication and data communication, after the line is connected with a communication partner, when a data communication signal is transmitted from the communication partner, a data communication is performed; and when a speech voice is transmitted, a bell sound is rung to call an operator for carrying out a speech communication.
However, even when the communication partner wants a speech communication, if an operator is absent, a communication charge is imposed on the partner although the speech communication fails.
In some case, a data communication signal or a speech voice is not properly detected.
Also, in some case, when a plurality of users share one communication apparatus, it is unknown which user is to answer an incoming call.
There is an apparatus which allows a confidential reception of data which is not wanted to be disclosed to others.
However, the confidential reception does not work unless a transmission side and a reception side agree about communication procedure.
U.S. Pat. No. 5,200,992 discloses a communication apparatus connected to a PBX extension line which identifies the type of a calling party side on receipt of an incoming call, i.e. discriminates between an intercom call and an outside call. This communication apparatus previously stores an ON time and an OFF time of a call signal from an extension line and a call signal from an outside line for comparison with an input call signal.
However, as the types of call signals increase, it is necessary for the communication apparatus to previously store an ON time and an OFF time for each of the types of call signals; hence, a memory for such storage is needed, and processing are complicated.